Up until now, scientists have believed that dinosaurs were split up into separate time periods and never shared the same eras. They were said to come about in the late Triassic period between 235 million to 200 million years ago. They thrived in the Jurassic period about 200 million to 120 million years ago. They were believed to have replaced their ancestors as soon as they died off. Then in 2003, the Silesaurus was discovered in Poland, showing that the dinosaurs’ ancestors may have survived into the Late Triassic period.

According to research found in northern New Mexico, it is now believed that the two species co-existed for tens of millions of years together, proving that the transition was a gradual process. This new theory is based on the findings of 1,3000 fossils including dinosaur bones, though there have been no complete skeletons found to this date. They have also found the ancestors of crocodiles, fish, and other amphibians 220 million to 210 million years ago. Some bones found were that of carnivores including Chindesaurus byransmalli who is related to a Triassic dinosaur named Coelophysis, two legged dinosaurs that resemble the Velociraptor. They’ve also found pieces of a Dromomeron romeri, a smaller version of the Lagerpeton. These findings were funded by the National Geographic Society, the Theodore Roosevelt Memorial Fund, and the Jurassic Foundation.

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